The present invention relates to a procedure and an installation for xe2x80x9cin situxe2x80x9d sensitization of water based explosives by means of the incorporation of air or gas in a non explosive or low sensitivity mixture of oxidants and fuels with the formation of an emulsion or dispersion of gas in liquid.
The mechanism of initiation of explosives by means of the generation of hot points due to the adiabatic compression of gas bubbles is the base of the modern industrial explosives formulated without components intrinsically explosive.
The introduction of gas bubbles can be made by the trapping during the mixture or by its formation through a chemical reaction. In the U.S. Pat. No. 3,400,026 a formulation which uses protein in solution (albumin, collagen, soy protein, etc.) in order to favour the formation of bubbles and their stabilization is described. The U.S. Pat. No. 3,582,411 describes a watergel explosive formulation which contains a foaming agent of the guar gum type modified by hydroxy groups.
In the U.S. Pat. No. 3,678,140 a process for the incorporation of air by means of the use of protein solution is described, passing the composition through a series of openings at pressures from 40 to 160 psi and simultaneously introducing air through eductors.
The gas bubbles incorporation by means of its generation as a result of a chemical reaction is described in the U.S. Pat. Nos. 3,706,607, 3,711,345, 3,713,919, 3,770,522, 3,790,415 and 3,886,010.
In relation to the manufacturing of the explosive in situ, that is, in the same truck used for the pumping of the explosive to the bores, the first patents are due to IRECO, such as it is described in the U.S. Pat. Nos. 3,303,738 and 3,338,033. These patents are characterized by the manufacturing in the truck of a watergel explosive by means of the dosification and mixture of oxidant salts liquid solution with a solid material which contains oxidant salts and thickeners. In U.S. Pat. No. 3,610,088 (IRECO) the same procedure of the previous patents are used for the formation of the watergel in situ and incorporate the simultaneous addition of air either by means of mechanical trapping or its generation through a chemical reaction. The EP patent 0 203 230 (IRECO) describes a mixer form by mobile and fixed blades which allows the manufacturing in situ of a blasting agent of water in oil emulsion type. The sensitizing of this emulsion is carried out by the addition of low density particles (oxidant or hollow microspheres).
The manufacturing of the explosive in situ has as main advantage the decreasing of the risk during the transport. In contrast it cannot be guaranteed the same levels of quality in the products as in the case of being manufactured in a manufacturing plant.
Another alternative is the transport of the finished product without sufficiently sensitizing, that is, at a density such that it has no capacity of propagating an stable detonation. In this context it has been generalized in the last years the transport of the base product and its sensitizing in mine either by mixing it with particulated nitrates of low density or mixtures of ammonium nitrates with hydrocarbons (ANFO) or through the generation of bubbles by means of a chemical reaction. The U.S. Pat. No. 4,555,278 describes an explosive of this type manufactured by mixing emulsion and ANFO. The European patent EP 0 194 775 describes an explosive of the type previously mentioned, formed starting from a base watergel.
The sensitizing of the base emulsion by generating bubbles of gas through chemical reaction is the widest used method at present. However in order to avoid the coalescence of the gas bubbles, such as it is described in the U.S. Pat. No. 4,008,108, the pumping and the handling of the emulsion should be carried out before the gasification reaction takes place. In this way, this method has the great disadvantage of having to wait a certain time from the filling of the holes until the final density is achieved, not having capacity of manoeuvre if the obtained density does not coincide with the expected one, being able to produce sensitizing failures or an incorrect distribution of the explosive in the bore hole column.